Commit 75820314 authored by Codrin Ciubotariu's avatar Codrin Ciubotariu Committed by Wolfram Sang
Browse files

i2c: core: add generic I2C GPIO recovery 



Multiple I2C bus drivers use similar bindings to obtain information needed
for I2C recovery. For example, for platforms using device-tree, the
properties look something like this:

&i2c {
	...
	pinctrl-names = "default", "gpio";
	pinctrl-0 = <&pinctrl_i2c_default>;
	pinctrl-1 = <&pinctrl_i2c_gpio>;
	sda-gpios = <&pio 0 GPIO_ACTIVE_HIGH>;
	scl-gpios = <&pio 1 (GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAIN)>;
	...
}

For this reason, we can add this common initialization in the core. This
way, other I2C bus drivers will be able to support GPIO recovery just by
providing a pointer to platform's pinctrl and calling i2c_recover_bus()
when SDA is stuck low.

Signed-off-by: default avatarCodrin Ciubotariu <codrin.ciubotariu@microchip.com>
[wsa: inverted one logic for better readability, minor update to kdoc]
Signed-off-by: default avatarWolfram Sang <wsa@kernel.org>
parent db36e827

drivers/i2c/i2c-core-base.c

+126 −0
Original line number Diff line number Diff line
@@ -32,6 +32,7 @@ 
#include <linux/of_device.h>

#include <linux/of.h>

#include <linux/of_irq.h>

#include <linux/pinctrl/consumer.h>

#include <linux/pm_domain.h>

#include <linux/pm_runtime.h>

#include <linux/pm_wakeirq.h>
@@ -181,6 +182,8 @@ int i2c_generic_scl_recovery(struct i2c_adapter *adap) 


	if (bri->prepare_recovery)

		bri->prepare_recovery(adap);

	if (bri->pinctrl)

		pinctrl_select_state(bri->pinctrl, bri->pins_gpio);



	/*

	 * If we can set SDA, we will always create a STOP to ensure additional
@@ -236,6 +239,8 @@ int i2c_generic_scl_recovery(struct i2c_adapter *adap) 


	if (bri->unprepare_recovery)

		bri->unprepare_recovery(adap);

	if (bri->pinctrl)

		pinctrl_select_state(bri->pinctrl, bri->pins_default);



	return ret;

}
@@ -251,6 +256,125 @@ int i2c_recover_bus(struct i2c_adapter *adap) 
}

EXPORT_SYMBOL_GPL(i2c_recover_bus);



static void i2c_gpio_init_pinctrl_recovery(struct i2c_adapter *adap)

{

	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;

	struct device *dev = &adap->dev;

	struct pinctrl *p = bri->pinctrl;



	/*

	 * we can't change states without pinctrl, so remove the states if

	 * populated

	 */

	if (!p) {

		bri->pins_default = NULL;

		bri->pins_gpio = NULL;

		return;

	}



	if (!bri->pins_default) {

		bri->pins_default = pinctrl_lookup_state(p,

							 PINCTRL_STATE_DEFAULT);

		if (IS_ERR(bri->pins_default)) {

			dev_dbg(dev, PINCTRL_STATE_DEFAULT " state not found for GPIO recovery\n");

			bri->pins_default = NULL;

		}

	}

	if (!bri->pins_gpio) {

		bri->pins_gpio = pinctrl_lookup_state(p, "gpio");

		if (IS_ERR(bri->pins_gpio))

			bri->pins_gpio = pinctrl_lookup_state(p, "recovery");



		if (IS_ERR(bri->pins_gpio)) {

			dev_dbg(dev, "no gpio or recovery state found for GPIO recovery\n");

			bri->pins_gpio = NULL;

		}

	}



	/* for pinctrl state changes, we need all the information */

	if (bri->pins_default && bri->pins_gpio) {

		dev_info(dev, "using pinctrl states for GPIO recovery");

	} else {

		bri->pinctrl = NULL;

		bri->pins_default = NULL;

		bri->pins_gpio = NULL;

	}

}



static int i2c_gpio_init_generic_recovery(struct i2c_adapter *adap)

{

	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;

	struct device *dev = &adap->dev;

	struct gpio_desc *gpiod;

	int ret = 0;



	/*

	 * don't touch the recovery information if the driver is not using

	 * generic SCL recovery

	 */

	if (bri->recover_bus && bri->recover_bus != i2c_generic_scl_recovery)

		return 0;



	/*

	 * pins might be taken as GPIO, so we should inform pinctrl about

	 * this and move the state to GPIO

	 */

	if (bri->pinctrl)

		pinctrl_select_state(bri->pinctrl, bri->pins_gpio);



	/*

	 * if there is incomplete or no recovery information, see if generic

	 * GPIO recovery is available

	 */

	if (!bri->scl_gpiod) {

		gpiod = devm_gpiod_get(dev, "scl", GPIOD_OUT_HIGH_OPEN_DRAIN);

		if (PTR_ERR(gpiod) == -EPROBE_DEFER) {

			ret  = -EPROBE_DEFER;

			goto cleanup_pinctrl_state;

		}

		if (!IS_ERR(gpiod)) {

			bri->scl_gpiod = gpiod;

			bri->recover_bus = i2c_generic_scl_recovery;

			dev_info(dev, "using generic GPIOs for recovery\n");

		}

	}



	/* SDA GPIOD line is optional, so we care about DEFER only */

	if (!bri->sda_gpiod) {

		/*

		 * We have SCL. Pull SCL low and wait a bit so that SDA glitches

		 * have no effect.

		 */

		gpiod_direction_output(bri->scl_gpiod, 0);

		udelay(10);

		gpiod = devm_gpiod_get(dev, "sda", GPIOD_IN);



		/* Wait a bit in case of a SDA glitch, and then release SCL. */

		udelay(10);

		gpiod_direction_output(bri->scl_gpiod, 1);



		if (PTR_ERR(gpiod) == -EPROBE_DEFER) {

			ret = -EPROBE_DEFER;

			goto cleanup_pinctrl_state;

		}

		if (!IS_ERR(gpiod))

			bri->sda_gpiod = gpiod;

	}



cleanup_pinctrl_state:

	/* change the state of the pins back to their default state */

	if (bri->pinctrl)

		pinctrl_select_state(bri->pinctrl, bri->pins_default);



	return ret;

}



static int i2c_gpio_init_recovery(struct i2c_adapter *adap)

{

	i2c_gpio_init_pinctrl_recovery(adap);

	return i2c_gpio_init_generic_recovery(adap);

}



static void i2c_init_recovery(struct i2c_adapter *adap)

{

	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
@@ -259,6 +383,8 @@ static void i2c_init_recovery(struct i2c_adapter *adap) 
	if (!bri)

		return;



	i2c_gpio_init_recovery(adap);



	if (!bri->recover_bus) {

		err_str = "no recover_bus() found";

		goto err;

include/linux/i2c.h

+11 −0
Original line number Diff line number Diff line
@@ -606,6 +606,14 @@ struct i2c_timings { 
 *	may configure padmux here for SDA/SCL line or something else they want.

 * @scl_gpiod: gpiod of the SCL line. Only required for GPIO recovery.

 * @sda_gpiod: gpiod of the SDA line. Only required for GPIO recovery.

 * @pinctrl: pinctrl used by GPIO recovery to change the state of the I2C pins.

 *      Optional.

 * @pins_default: default pinctrl state of SCL/SDA lines, when they are assigned

 *      to the I2C bus. Optional. Populated internally for GPIO recovery, if

 *      state with the name PINCTRL_STATE_DEFAULT is found and pinctrl is valid.

 * @pins_gpio: recovery pinctrl state of SCL/SDA lines, when they are used as

 *      GPIOs. Optional. Populated internally for GPIO recovery, if this state

 *      is called "gpio" or "recovery" and pinctrl is valid.

 */

struct i2c_bus_recovery_info {

	int (*recover_bus)(struct i2c_adapter *adap);
@@ -622,6 +630,9 @@ struct i2c_bus_recovery_info { 
	/* gpio recovery */

	struct gpio_desc *scl_gpiod;

	struct gpio_desc *sda_gpiod;

	struct pinctrl *pinctrl;

	struct pinctrl_state *pins_default;

	struct pinctrl_state *pins_gpio;

};



int i2c_recover_bus(struct i2c_adapter *adap);